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Old 06-03-2019, 11:57 AM   #21
R_J
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Default Re: Help with dead Commodore 1802

The sound (bong noise) is the degausing coil, mesure the DC voltage across the filter caps, C814 (12v) and C813 (121V) the heatsinks may not be grounded. If there are no voltages, then its time to start checking on the primary side.
What voltage do you measure ACROSS C803? If you have voltage across C803, leave your negative meter lead on C803 negative and with the red probe check the voltage on T801 pin 4 and pin 2

Last edited by R_J; 06-03-2019 at 12:04 PM..
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Old 06-03-2019, 01:03 PM   #22
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Default Re: Help with dead Commodore 1802

Quote:
Originally Posted by R_J View Post
The sound (bong noise) is the degausing coil, mesure the DC voltage across the filter caps, C814 (12v) and C813 (121V) the heatsinks may not be grounded. If there are no voltages, then its time to start checking on the primary side.
What voltage do you measure ACROSS C803? If you have voltage across C803, leave your negative meter lead on C803 negative and with the red probe check the voltage on T801 pin 4 and pin 2
Couldnt find C814 anywhere until i noticed it was a cap labeled as R814. Anyway no voltage across C813 & C814 and no voltage between C803 and pins 4 & 2 of T801

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Old 06-03-2019, 03:30 PM   #23
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Default Re: Help with dead Commodore 1802

So you have 0 voltage the main filter capacitor, that does'nt leave much, Check the large 3.3Ω 10 watt resistor R801, it must be open or has cold solder connections
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File Type: jpg 1802_tps.JPG (171.6 KB, 4 views)
File Type: jpg ac path to dc.JPG (194.5 KB, 1 views)

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Old 06-04-2019, 03:59 AM   #24
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Default Re: Help with dead Commodore 1802

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So you have 0 voltage the main filter capacitor, that does'nt leave much, Check the large 3.3Ω 10 watt resistor R801, it must be open or has cold solder connections
R801 is open circuit and registers nothing on any scale.
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Old 06-04-2019, 11:03 AM   #25
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Default Re: Help with dead Commodore 1802

I only had a 4.7ohm wire wound resistor here and ordered some I thought were 10A 3 Ohms that were actualy 3.3ohms. Ive got another 10A 3ohm one comming and be here in a few days or so.
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Old 06-04-2019, 11:28 AM   #26
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Default Re: Help with dead Commodore 1802

3.3Ω 10 watt not, 10 amp, the 4.7Ω would work to test if it is around 10watt
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Old 06-04-2019, 01:03 PM   #27
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Default Re: Help with dead Commodore 1802

R801 is probably metal oxide, not wirewound.
a wirewound will get glowy hot instead of going open-circuit.
smash the old one to check the insides.

so now you need to see what made it burn!
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Old 06-04-2019, 01:48 PM   #28
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Default Re: Help with dead Commodore 1802

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R801 is probably metal oxide, not wirewound.
a wirewound will get glowy hot instead of going open-circuit.
smash the old one to check the insides.

so now you need to see what made it burn!
Its a large white oblong ceramic type.
Could it be just age and maybe being left turned on for hours because I accidently did that when I left it on overnight one night by accident. It was after that I found it dead.

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Old 06-04-2019, 02:09 PM   #29
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Default Re: Help with dead Commodore 1802

This is it. Is it. What type is it?
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Old 06-04-2019, 02:38 PM   #30
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Default Re: Help with dead Commodore 1802

you cant tell without breaking it, but you rarely get wirewounds used on ac because the coil radiates interference.

btw, the replacement needs airflow under it, what we used to do is solder the new one on top of the dead one so it still stands high off the board.
that or use ceramic spacers.

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Old 06-04-2019, 05:27 PM   #31
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Default Re: Help with dead Commodore 1802

It will be a wirewound, this from digikey should work A137101-ND Mfg # SQZW103R3J which seems to be like the original. TYPE SQZ horizontal, pluggable.
They go open after time, the wire gets a weak spot and thats it, If there was any other problem it would have blown the fuse and not the resistor.
If you just want to try the monitor, replace it with a piece of wire, if there is a short anywhere the fuse will blow. or if you want to get fancy replace it with a incandescent lamp to test

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Old 06-05-2019, 05:09 AM   #32
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Default Re: Help with dead Commodore 1802

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It will be a wirewound, this from digikey should work A137101-ND Mfg # SQZW103R3J which seems to be like the original. TYPE SQZ horizontal, pluggable.
They go open after time, the wire gets a weak spot and thats it, If there was any other problem it would have blown the fuse and not the resistor.
If you just want to try the monitor, replace it with a piece of wire, if there is a short anywhere the fuse will blow. or if you want to get fancy replace it with a incandescent lamp to test
wow thats expensive..

Subtotal: 2.07
Shipping: 12.00
VAT: 2.81
Total: 16.88

ive got a few ceramic wire wound ones coming from Ebay and yesterday after lots of searching I also found and purchased a MOX one as well. Is the MOX a better one to use?
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Old 06-05-2019, 05:20 AM   #33
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Default Re: Help with dead Commodore 1802

where the fuck are you shopping?????

RS is free delivery,
germany and poland only cost about 6
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Old 06-05-2019, 05:33 AM   #34
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Default Re: Help with dead Commodore 1802

https://uk.rs-online.com/web/p/throu...stors/6661718/
7.90 inc free postage.

https://www.tme.eu/gb/details/crl10w...s/sr-passives/
55p + about 6 postage

https://www.reichelt.com/gb/en/wirew...?&trstct=pol_0
87p + postage
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Old 06-05-2019, 11:02 AM   #35
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Default Re: Help with dead Commodore 1802

The resistor is just to provide a bit of surge protection when you first turn it on. It is in the ac line, it can be made from anything, its not important.
I just used digikey to find a mfg. part number of the same type and mounting that you are replacing.

https://uk.farnell.com/international...10w/dp/1457934 0.933

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Old 06-05-2019, 12:18 PM   #36
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Default Re: Help with dead Commodore 1802

Quote:
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where the fuck are you shopping?????

RS is free delivery,
germany and poland only cost about 6
That was DigiKey.

Ive got some wirewound coming from a trader on Ebay for few quid.
I will do as you said and solder in on top of the original.
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Old 06-06-2019, 02:36 PM   #37
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Default Re: Help with dead Commodore 1802

I fitted a 3.3 ohm wire wound resistor and as soon as I powered it up it blew it again.
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Old 06-06-2019, 02:53 PM   #38
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Default Re: Help with dead Commodore 1802

It blew the 3.3Ω 10 watt resistor! but not the fuse? Ok check the 4 power supply diodes, then check the resistance across the main capacitor. You must have a dead short somewhere in the primary circuit
Post a picture of that new resistor that blew open

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Old 06-06-2019, 03:20 PM   #39
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Default Re: Help with dead Commodore 1802

told you!
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Old 06-07-2019, 05:37 AM   #40
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Default Re: Help with dead Commodore 1802

Quote:
Originally Posted by stj View Post
R801 is probably metal oxide, not wirewound.
a wirewound will get glowy hot instead of going open-circuit.
smash the old one to check the insides.

so now you need to see what made it burn!
Hhahhaha yep You said it! Do you still think it a MOX because I did order a couple of these wire wound ones and a MOX one that I am still waiting to arrive. I will now do like RJ said and rty and find that short. I never expected that. there was just I small flash from the new restistor and I knew straight away and yep! its was blown. Just as well I got another.
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